1 /*
2 * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/classLoaderDataGraph.inline.hpp"
27 #include "classfile/dictionary.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "code/codeCache.hpp"
32 #include "code/icBuffer.hpp"
33 #include "code/nmethod.hpp"
34 #include "code/pcDesc.hpp"
35 #include "code/scopeDesc.hpp"
36 #include "gc/shared/collectedHeap.hpp"
37 #include "gc/shared/gcLocker.hpp"
38 #include "gc/shared/oopStorage.hpp"
39 #include "gc/shared/strongRootsScope.hpp"
40 #include "gc/shared/workgroup.hpp"
41 #include "interpreter/interpreter.hpp"
42 #include "jfr/jfrEvents.hpp"
43 #include "logging/log.hpp"
44 #include "logging/logStream.hpp"
45 #include "memory/resourceArea.hpp"
46 #include "memory/universe.hpp"
47 #include "oops/oop.inline.hpp"
48 #include "oops/symbol.hpp"
49 #include "runtime/atomic.hpp"
50 #include "runtime/compilationPolicy.hpp"
51 #include "runtime/deoptimization.hpp"
52 #include "runtime/frame.inline.hpp"
53 #include "runtime/handles.inline.hpp"
54 #include "runtime/interfaceSupport.inline.hpp"
55 #include "runtime/mutexLocker.hpp"
56 #include "runtime/orderAccess.hpp"
57 #include "runtime/osThread.hpp"
58 #include "runtime/safepoint.hpp"
59 #include "runtime/safepointMechanism.inline.hpp"
60 #include "runtime/signature.hpp"
61 #include "runtime/stubCodeGenerator.hpp"
62 #include "runtime/stubRoutines.hpp"
63 #include "runtime/sweeper.hpp"
64 #include "runtime/synchronizer.hpp"
65 #include "runtime/thread.inline.hpp"
66 #include "runtime/threadSMR.hpp"
67 #include "runtime/timerTrace.hpp"
68 #include "services/runtimeService.hpp"
69 #include "utilities/events.hpp"
70 #include "utilities/macros.hpp"
71
72 static void post_safepoint_begin_event(EventSafepointBegin& event,
73 uint64_t safepoint_id,
74 int thread_count,
75 int critical_thread_count) {
76 if (event.should_commit()) {
77 event.set_safepointId(safepoint_id);
78 event.set_totalThreadCount(thread_count);
79 event.set_jniCriticalThreadCount(critical_thread_count);
80 event.commit();
81 }
82 }
83
84 static void post_safepoint_cleanup_event(EventSafepointCleanup& event, uint64_t safepoint_id) {
85 if (event.should_commit()) {
86 event.set_safepointId(safepoint_id);
87 event.commit();
88 }
89 }
90
91 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization& event,
92 uint64_t safepoint_id,
93 int initial_number_of_threads,
94 int threads_waiting_to_block,
95 uint64_t iterations) {
96 if (event.should_commit()) {
97 event.set_safepointId(safepoint_id);
98 event.set_initialThreadCount(initial_number_of_threads);
99 event.set_runningThreadCount(threads_waiting_to_block);
100 event.set_iterations(iterations);
101 event.commit();
102 }
103 }
104
105 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask& event,
106 uint64_t safepoint_id,
107 const char* name) {
108 if (event.should_commit()) {
109 event.set_safepointId(safepoint_id);
110 event.set_name(name);
111 event.commit();
112 }
113 }
114
115 static void post_safepoint_end_event(EventSafepointEnd& event, uint64_t safepoint_id) {
116 if (event.should_commit()) {
117 event.set_safepointId(safepoint_id);
118 event.commit();
119 }
120 }
121
122 // SafepointCheck
123 SafepointStateTracker::SafepointStateTracker(uint64_t safepoint_id, bool at_safepoint)
124 : _safepoint_id(safepoint_id), _at_safepoint(at_safepoint) {}
125
126 bool SafepointStateTracker::safepoint_state_changed() {
127 return _safepoint_id != SafepointSynchronize::safepoint_id() ||
128 _at_safepoint != SafepointSynchronize::is_at_safepoint();
129 }
130
131 // --------------------------------------------------------------------------------------------------
132 // Implementation of Safepoint begin/end
133
134 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
135 int SafepointSynchronize::_waiting_to_block = 0;
136 volatile uint64_t SafepointSynchronize::_safepoint_counter = 0;
137 uint64_t SafepointSynchronize::_safepoint_id = 0;
138 const uint64_t SafepointSynchronize::InactiveSafepointCounter = 0;
139 int SafepointSynchronize::_current_jni_active_count = 0;
140
141 WaitBarrier* SafepointSynchronize::_wait_barrier;
142
143 static volatile bool PageArmed = false; // safepoint polling page is RO|RW vs PROT_NONE
144 static bool timeout_error_printed = false;
145
146 // Statistic related
147 static jlong _safepoint_begin_time = 0;
148 static volatile int _nof_threads_hit_polling_page = 0;
149
150 void SafepointSynchronize::init(Thread* vmthread) {
151 // WaitBarrier should never be destroyed since we will have
152 // threads waiting on it while exiting.
153 _wait_barrier = new WaitBarrier(vmthread);
154 SafepointTracing::init();
155 }
156
157 void SafepointSynchronize::increment_jni_active_count() {
158 assert(Thread::current()->is_VM_thread(), "Only VM thread may increment");
159 ++_current_jni_active_count;
160 }
161
162 void SafepointSynchronize::decrement_waiting_to_block() {
163 assert(_waiting_to_block > 0, "sanity check");
164 assert(Thread::current()->is_VM_thread(), "Only VM thread may decrement");
165 --_waiting_to_block;
166 }
167
168 bool SafepointSynchronize::thread_not_running(ThreadSafepointState *cur_state) {
169 if (!cur_state->is_running()) {
170 return true;
171 }
172 cur_state->examine_state_of_thread(SafepointSynchronize::safepoint_counter());
173 if (!cur_state->is_running()) {
174 return true;
175 }
176 LogTarget(Trace, safepoint) lt;
177 if (lt.is_enabled()) {
178 ResourceMark rm;
179 LogStream ls(lt);
180 cur_state->print_on(&ls);
181 }
182 return false;
183 }
184
185 #ifdef ASSERT
186 static void assert_list_is_valid(const ThreadSafepointState* tss_head, int still_running) {
187 int a = 0;
188 const ThreadSafepointState *tmp_tss = tss_head;
189 while (tmp_tss != NULL) {
190 ++a;
191 assert(tmp_tss->is_running(), "Illegal initial state");
192 tmp_tss = tmp_tss->get_next();
193 }
194 assert(a == still_running, "Must be the same");
195 }
196 #endif // ASSERT
197
198 static void back_off(int64_t start_time) {
199 // We start with fine-grained nanosleeping until a millisecond has
200 // passed, at which point we resort to plain naked_short_sleep.
201 if (os::javaTimeNanos() - start_time < NANOSECS_PER_MILLISEC) {
202 os::naked_short_nanosleep(10 * (NANOUNITS / MICROUNITS));
203 } else {
204 os::naked_short_sleep(1);
205 }
206 }
207
208 int SafepointSynchronize::synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running)
209 {
210 JavaThreadIteratorWithHandle jtiwh;
211
212 #ifdef ASSERT
213 for (; JavaThread *cur = jtiwh.next(); ) {
214 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
215 }
216 jtiwh.rewind();
217 #endif // ASSERT
218
219 // Iterate through all threads until it has been determined how to stop them all at a safepoint.
220 int still_running = nof_threads;
221 ThreadSafepointState *tss_head = NULL;
222 ThreadSafepointState **p_prev = &tss_head;
223 for (; JavaThread *cur = jtiwh.next(); ) {
224 ThreadSafepointState *cur_tss = cur->safepoint_state();
225 assert(cur_tss->get_next() == NULL, "Must be NULL");
226 if (thread_not_running(cur_tss)) {
227 --still_running;
228 } else {
229 *p_prev = cur_tss;
230 p_prev = cur_tss->next_ptr();
231 }
232 }
233 *p_prev = NULL;
234
235 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
236
237 *initial_running = still_running;
238
239 // If there is no thread still running, we are already done.
240 if (still_running <= 0) {
241 assert(tss_head == NULL, "Must be empty");
242 return 1;
243 }
244
245 int iterations = 1; // The first iteration is above.
246 int64_t start_time = os::javaTimeNanos();
247
248 do {
249 // Check if this has taken too long:
250 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
251 print_safepoint_timeout();
252 }
253 if (int(iterations) == -1) { // overflow - something is wrong.
254 // We can only overflow here when we are using global
255 // polling pages. We keep this guarantee in its original
256 // form so that searches of the bug database for this
257 // failure mode find the right bugs.
258 guarantee (!PageArmed, "invariant");
259 }
260
261 p_prev = &tss_head;
262 ThreadSafepointState *cur_tss = tss_head;
263 while (cur_tss != NULL) {
264 assert(cur_tss->is_running(), "Illegal initial state");
265 if (thread_not_running(cur_tss)) {
266 --still_running;
267 *p_prev = NULL;
268 ThreadSafepointState *tmp = cur_tss;
269 cur_tss = cur_tss->get_next();
270 tmp->set_next(NULL);
271 } else {
272 *p_prev = cur_tss;
273 p_prev = cur_tss->next_ptr();
274 cur_tss = cur_tss->get_next();
275 }
276 }
277
278 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
279
280 if (still_running > 0) {
281 back_off(start_time);
282 }
283
284 iterations++;
285 } while (still_running > 0);
286
287 assert(tss_head == NULL, "Must be empty");
288
289 return iterations;
290 }
291
292 void SafepointSynchronize::arm_safepoint() {
293 // Begin the process of bringing the system to a safepoint.
294 // Java threads can be in several different states and are
295 // stopped by different mechanisms:
296 //
297 // 1. Running interpreted
298 // When executing branching/returning byte codes interpreter
299 // checks if the poll is armed, if so blocks in SS::block().
300 // When using global polling the interpreter dispatch table
301 // is changed to force it to check for a safepoint condition
302 // between bytecodes.
303 // 2. Running in native code
304 // When returning from the native code, a Java thread must check
305 // the safepoint _state to see if we must block. If the
306 // VM thread sees a Java thread in native, it does
307 // not wait for this thread to block. The order of the memory
308 // writes and reads of both the safepoint state and the Java
309 // threads state is critical. In order to guarantee that the
310 // memory writes are serialized with respect to each other,
311 // the VM thread issues a memory barrier instruction.
312 // 3. Running compiled Code
313 // Compiled code reads the local polling page that
314 // is set to fault if we are trying to get to a safepoint.
315 // 4. Blocked
316 // A thread which is blocked will not be allowed to return from the
317 // block condition until the safepoint operation is complete.
318 // 5. In VM or Transitioning between states
319 // If a Java thread is currently running in the VM or transitioning
320 // between states, the safepointing code will poll the thread state
321 // until the thread blocks itself when it attempts transitions to a
322 // new state or locking a safepoint checked monitor.
323
324 // We must never miss a thread with correct safepoint id, so we must make sure we arm
325 // the wait barrier for the next safepoint id/counter.
326 // Arming must be done after resetting _current_jni_active_count, _waiting_to_block.
327 _wait_barrier->arm(static_cast<int>(_safepoint_counter + 1));
328
329 assert((_safepoint_counter & 0x1) == 0, "must be even");
330 // The store to _safepoint_counter must happen after any stores in arming.
331 OrderAccess::release_store(&_safepoint_counter, _safepoint_counter + 1);
332
333 // We are synchronizing
334 OrderAccess::storestore(); // Ordered with _safepoint_counter
335 _state = _synchronizing;
336
337 if (SafepointMechanism::uses_thread_local_poll()) {
338 // Arming the per thread poll while having _state != _not_synchronized means safepointing
339 log_trace(safepoint)("Setting thread local yield flag for threads");
340 OrderAccess::storestore(); // storestore, global state -> local state
341 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
342 // Make sure the threads start polling, it is time to yield.
343 SafepointMechanism::arm_local_poll(cur);
344 }
345 }
346 OrderAccess::fence(); // storestore|storeload, global state -> local state
347
348 if (SafepointMechanism::uses_global_page_poll()) {
349 // Make interpreter safepoint aware
350 Interpreter::notice_safepoints();
351
352 // Make polling safepoint aware
353 guarantee (!PageArmed, "invariant") ;
354 PageArmed = true;
355 os::make_polling_page_unreadable();
356 }
357 }
358
359 // Roll all threads forward to a safepoint and suspend them all
360 void SafepointSynchronize::begin() {
361 assert(Thread::current()->is_VM_thread(), "Only VM thread may execute a safepoint");
362
363 EventSafepointBegin begin_event;
364 SafepointTracing::begin(VMThread::vm_op_type());
365
366 Universe::heap()->safepoint_synchronize_begin();
367
368 // By getting the Threads_lock, we assure that no threads are about to start or
369 // exit. It is released again in SafepointSynchronize::end().
370 Threads_lock->lock();
371
372 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
373
374 int nof_threads = Threads::number_of_threads();
375
376 _nof_threads_hit_polling_page = 0;
377
378 log_debug(safepoint)("Safepoint synchronization initiated using %s wait barrier. (%d threads)", _wait_barrier->description(), nof_threads);
379
380 // Reset the count of active JNI critical threads
381 _current_jni_active_count = 0;
382
383 // Set number of threads to wait for
384 _waiting_to_block = nof_threads;
385
386 jlong safepoint_limit_time = 0;
387 if (SafepointTimeout) {
388 // Set the limit time, so that it can be compared to see if this has taken
389 // too long to complete.
390 safepoint_limit_time = SafepointTracing::start_of_safepoint() + (jlong)SafepointTimeoutDelay * (NANOUNITS / MILLIUNITS);
391 timeout_error_printed = false;
392 }
393
394 EventSafepointStateSynchronization sync_event;
395 int initial_running = 0;
396
397 // Arms the safepoint, _current_jni_active_count and _waiting_to_block must be set before.
398 arm_safepoint();
399
400 // Will spin until all threads are safe.
401 int iterations = synchronize_threads(safepoint_limit_time, nof_threads, &initial_running);
402 assert(_waiting_to_block == 0, "No thread should be running");
403
404 #ifndef PRODUCT
405 if (safepoint_limit_time != 0) {
406 jlong current_time = os::javaTimeNanos();
407 if (safepoint_limit_time < current_time) {
408 log_warning(safepoint)("# SafepointSynchronize: Finished after "
409 INT64_FORMAT_W(6) " ms",
410 (int64_t)(current_time - SafepointTracing::start_of_safepoint()) / (NANOUNITS / MILLIUNITS));
411 }
412 }
413 #endif
414
415 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
416
417 // Record state
418 _state = _synchronized;
419
420 OrderAccess::fence();
421
422 // Set the new id
423 ++_safepoint_id;
424
425 #ifdef ASSERT
426 // Make sure all the threads were visited.
427 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
428 assert(cur->was_visited_for_critical_count(_safepoint_counter), "missed a thread");
429 }
430 #endif // ASSERT
431
432 // Update the count of active JNI critical regions
433 GCLocker::set_jni_lock_count(_current_jni_active_count);
434
435 post_safepoint_synchronize_event(sync_event,
436 _safepoint_id,
437 initial_running,
438 _waiting_to_block, iterations);
439
440 SafepointTracing::synchronized(nof_threads, initial_running, _nof_threads_hit_polling_page);
441
442 // We do the safepoint cleanup first since a GC related safepoint
443 // needs cleanup to be completed before running the GC op.
444 EventSafepointCleanup cleanup_event;
445 do_cleanup_tasks();
446 post_safepoint_cleanup_event(cleanup_event, _safepoint_id);
447
448 post_safepoint_begin_event(begin_event, _safepoint_id, nof_threads, _current_jni_active_count);
449 SafepointTracing::cleanup();
450 }
451
452 void SafepointSynchronize::disarm_safepoint() {
453 uint64_t active_safepoint_counter = _safepoint_counter;
454 {
455 JavaThreadIteratorWithHandle jtiwh;
456 #ifdef ASSERT
457 // A pending_exception cannot be installed during a safepoint. The threads
458 // may install an async exception after they come back from a safepoint into
459 // pending_exception after they unblock. But that should happen later.
460 for (; JavaThread *cur = jtiwh.next(); ) {
461 assert (!(cur->has_pending_exception() &&
462 cur->safepoint_state()->is_at_poll_safepoint()),
463 "safepoint installed a pending exception");
464 }
465 #endif // ASSERT
466
467 if (SafepointMechanism::uses_global_page_poll()) {
468 guarantee (PageArmed, "invariant");
469 // Make polling safepoint aware
470 os::make_polling_page_readable();
471 PageArmed = false;
472 // Remove safepoint check from interpreter
473 Interpreter::ignore_safepoints();
474 }
475
476 OrderAccess::fence(); // keep read and write of _state from floating up
477 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
478
479 // Change state first to _not_synchronized.
480 // No threads should see _synchronized when running.
481 _state = _not_synchronized;
482
483 // Set the next dormant (even) safepoint id.
484 assert((_safepoint_counter & 0x1) == 1, "must be odd");
485 OrderAccess::release_store(&_safepoint_counter, _safepoint_counter + 1);
486
487 OrderAccess::fence(); // Keep the local state from floating up.
488
489 jtiwh.rewind();
490 for (; JavaThread *current = jtiwh.next(); ) {
491 // Clear the visited flag to ensure that the critical counts are collected properly.
492 DEBUG_ONLY(current->reset_visited_for_critical_count(active_safepoint_counter);)
493 ThreadSafepointState* cur_state = current->safepoint_state();
494 assert(!cur_state->is_running(), "Thread not suspended at safepoint");
495 cur_state->restart(); // TSS _running
496 assert(cur_state->is_running(), "safepoint state has not been reset");
497
498 SafepointMechanism::disarm_if_needed(current, false /* NO release */);
499 }
500 } // ~JavaThreadIteratorWithHandle
501
502 // Release threads lock, so threads can be created/destroyed again.
503 Threads_lock->unlock();
504
505 // Wake threads after local state is correctly set.
506 _wait_barrier->disarm();
507 }
508
509 // Wake up all threads, so they are ready to resume execution after the safepoint
510 // operation has been carried out
511 void SafepointSynchronize::end() {
512 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
513 EventSafepointEnd event;
514 assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint");
515
516 disarm_safepoint();
517
518 Universe::heap()->safepoint_synchronize_end();
519
520 SafepointTracing::end();
521
522 post_safepoint_end_event(event, safepoint_id());
523 }
524
525 bool SafepointSynchronize::is_cleanup_needed() {
526 // Need a safepoint if there are many monitors to deflate.
527 if (ObjectSynchronizer::is_cleanup_needed()) return true;
528 // Need a safepoint if some inline cache buffers is non-empty
529 if (!InlineCacheBuffer::is_empty()) return true;
530 if (StringTable::needs_rehashing()) return true;
531 if (SymbolTable::needs_rehashing()) return true;
532 return false;
533 }
534
535 class ParallelSPCleanupThreadClosure : public ThreadClosure {
536 private:
537 CodeBlobClosure* _nmethod_cl;
538 DeflateMonitorCounters* _counters;
539
540 public:
541 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
542 _nmethod_cl(UseCodeAging ? NMethodSweeper::prepare_reset_hotness_counters() : NULL),
543 _counters(counters) {}
544
545 void do_thread(Thread* thread) {
546 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
547 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
548 ! thread->is_Code_cache_sweeper_thread()) {
549 JavaThread* jt = (JavaThread*) thread;
550 jt->nmethods_do(_nmethod_cl);
551 }
552 }
553 };
554
555 class ParallelSPCleanupTask : public AbstractGangTask {
556 private:
557 SubTasksDone _subtasks;
558 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
559 uint _num_workers;
560 DeflateMonitorCounters* _counters;
561 public:
562 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
563 AbstractGangTask("Parallel Safepoint Cleanup"),
564 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
565 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
566 _num_workers(num_workers),
567 _counters(counters) {}
568
569 void work(uint worker_id) {
570 uint64_t safepoint_id = SafepointSynchronize::safepoint_id();
571 // All threads deflate monitors and mark nmethods (if necessary).
572 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
573
574 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
575 const char* name = "deflating global idle monitors";
576 EventSafepointCleanupTask event;
577 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
578 ObjectSynchronizer::deflate_idle_monitors(_counters);
579
580 post_safepoint_cleanup_task_event(event, safepoint_id, name);
581 }
582
583 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
584 const char* name = "updating inline caches";
585 EventSafepointCleanupTask event;
586 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
587 InlineCacheBuffer::update_inline_caches();
588
589 post_safepoint_cleanup_task_event(event, safepoint_id, name);
590 }
591
592 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
593 const char* name = "compilation policy safepoint handler";
594 EventSafepointCleanupTask event;
595 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
596 CompilationPolicy::policy()->do_safepoint_work();
597
598 post_safepoint_cleanup_task_event(event, safepoint_id, name);
599 }
600
601 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
602 if (SymbolTable::needs_rehashing()) {
603 const char* name = "rehashing symbol table";
604 EventSafepointCleanupTask event;
605 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
606 SymbolTable::rehash_table();
607
608 post_safepoint_cleanup_task_event(event, safepoint_id, name);
609 }
610 }
611
612 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
613 if (StringTable::needs_rehashing()) {
614 const char* name = "rehashing string table";
615 EventSafepointCleanupTask event;
616 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
617 StringTable::rehash_table();
618
619 post_safepoint_cleanup_task_event(event, safepoint_id, name);
620 }
621 }
622
623 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
624 if (ClassLoaderDataGraph::should_purge_and_reset()) {
625 // CMS delays purging the CLDG until the beginning of the next safepoint and to
626 // make sure concurrent sweep is done
627 const char* name = "purging class loader data graph";
628 EventSafepointCleanupTask event;
629 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
630 ClassLoaderDataGraph::purge();
631
632 post_safepoint_cleanup_task_event(event, safepoint_id, name);
633 }
634 }
635
636 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
637 if (Dictionary::does_any_dictionary_needs_resizing()) {
638 const char* name = "resizing system dictionaries";
639 EventSafepointCleanupTask event;
640 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
641 ClassLoaderDataGraph::resize_dictionaries();
642
643 post_safepoint_cleanup_task_event(event, safepoint_id, name);
644 }
645 }
646
647 if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP)) {
648 // Don't bother reporting event or time for this very short operation.
649 // To have any utility we'd also want to report whether needed.
650 OopStorage::trigger_cleanup_if_needed();
651 }
652
653 _subtasks.all_tasks_completed(_num_workers);
654 }
655 };
656
657 // Various cleaning tasks that should be done periodically at safepoints.
658 void SafepointSynchronize::do_cleanup_tasks() {
659
660 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
661
662 // Prepare for monitor deflation.
663 DeflateMonitorCounters deflate_counters;
664 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
665
666 CollectedHeap* heap = Universe::heap();
667 assert(heap != NULL, "heap not initialized yet?");
668 WorkGang* cleanup_workers = heap->get_safepoint_workers();
669 if (cleanup_workers != NULL) {
670 // Parallel cleanup using GC provided thread pool.
671 uint num_cleanup_workers = cleanup_workers->active_workers();
672 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
673 StrongRootsScope srs(num_cleanup_workers);
674 cleanup_workers->run_task(&cleanup);
675 } else {
676 // Serial cleanup using VMThread.
677 ParallelSPCleanupTask cleanup(1, &deflate_counters);
678 StrongRootsScope srs(1);
679 cleanup.work(0);
680 }
681
682 // Needs to be done single threaded by the VMThread. This walks
683 // the thread stacks looking for references to metadata before
684 // deciding to remove it from the metaspaces.
685 if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) {
686 const char* name = "cleanup live ClassLoaderData metaspaces";
687 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
688 ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
689 }
690
691 // Finish monitor deflation.
692 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
693
694 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
695 }
696
697 // Methods for determining if a JavaThread is safepoint safe.
698
699 // False means unsafe with undetermined state.
700 // True means a determined state, but it may be an unsafe state.
701 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter.
702 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) {
703 assert((safepoint_count != InactiveSafepointCounter &&
704 Thread::current() == (Thread*)VMThread::vm_thread() &&
705 SafepointSynchronize::_state != _not_synchronized)
706 || safepoint_count == InactiveSafepointCounter, "Invalid check");
707
708 // To handle the thread_blocked state on the backedge of the WaitBarrier from
709 // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we
710 // re-read state after we read thread safepoint id. The JavaThread changes its
711 // thread state from thread_blocked before resetting safepoint id to 0.
712 // This guarantees the second read will be from an updated thread state. It can
713 // either be different state making this an unsafe state or it can see blocked
714 // again. When we see blocked twice with a 0 safepoint id, either:
715 // - It is normally blocked, e.g. on Mutex, TBIVM.
716 // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier.
717 // - It was in SS:block() but now on a Mutex.
718 // All of these cases are safe.
719
720 *state = thread->thread_state();
721 OrderAccess::loadload();
722 uint64_t sid = thread->safepoint_state()->get_safepoint_id(); // Load acquire
723 if (sid != InactiveSafepointCounter && sid != safepoint_count) {
724 // In an old safepoint, state not relevant.
725 return false;
726 }
727 return *state == thread->thread_state();
728 }
729
730 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) {
731 switch(state) {
732 case _thread_in_native:
733 // native threads are safe if they have no java stack or have walkable stack
734 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
735
736 case _thread_blocked:
737 // On wait_barrier or blocked.
738 // Blocked threads should already have walkable stack.
739 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
740 return true;
741
742 default:
743 return false;
744 }
745 }
746
747 bool SafepointSynchronize::handshake_safe(JavaThread *thread) {
748 // This function must be called with the Threads_lock held so an externally
749 // suspended thread cannot be resumed thus it is safe.
750 assert(Threads_lock->owned_by_self() && Thread::current()->is_VM_thread(),
751 "Must hold Threads_lock and be VMThread");
752 if (thread->is_ext_suspended() || thread->is_terminated()) {
753 return true;
754 }
755 JavaThreadState stable_state;
756 if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) {
757 return safepoint_safe_with(thread, stable_state);
758 }
759 return false;
760 }
761
762 // See if the thread is running inside a lazy critical native and
763 // update the thread critical count if so. Also set a suspend flag to
764 // cause the native wrapper to return into the JVM to do the unlock
765 // once the native finishes.
766 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
767 if (state == _thread_in_native &&
768 thread->has_last_Java_frame() &&
769 thread->frame_anchor()->walkable()) {
770 // This thread might be in a critical native nmethod so look at
771 // the top of the stack and increment the critical count if it
772 // is.
773 frame wrapper_frame = thread->last_frame();
774 CodeBlob* stub_cb = wrapper_frame.cb();
775 if (stub_cb != NULL &&
776 stub_cb->is_nmethod() &&
777 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
778 // A thread could potentially be in a critical native across
779 // more than one safepoint, so only update the critical state on
780 // the first one. When it returns it will perform the unlock.
781 if (!thread->do_critical_native_unlock()) {
782 #ifdef ASSERT
783 if (!thread->in_critical()) {
784 GCLocker::increment_debug_jni_lock_count();
785 }
786 #endif
787 thread->enter_critical();
788 // Make sure the native wrapper calls back on return to
789 // perform the needed critical unlock.
790 thread->set_critical_native_unlock();
791 }
792 }
793 }
794 }
795
796 // -------------------------------------------------------------------------------------------------------
797 // Implementation of Safepoint blocking point
798
799 void SafepointSynchronize::block(JavaThread *thread) {
800 assert(thread != NULL, "thread must be set");
801 assert(thread->is_Java_thread(), "not a Java thread");
802
803 // Threads shouldn't block if they are in the middle of printing, but...
804 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
805
806 // Only bail from the block() call if the thread is gone from the
807 // thread list; starting to exit should still block.
808 if (thread->is_terminated()) {
809 // block current thread if we come here from native code when VM is gone
810 thread->block_if_vm_exited();
811
812 // otherwise do nothing
813 return;
814 }
815
816 JavaThreadState state = thread->thread_state();
817 thread->frame_anchor()->make_walkable(thread);
818
819 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
820 // Check that we have a valid thread_state at this point
821 switch(state) {
822 case _thread_in_vm_trans:
823 case _thread_in_Java: // From compiled code
824 case _thread_in_native_trans:
825 case _thread_blocked_trans:
826 case _thread_new_trans:
827
828 // We have no idea where the VMThread is, it might even be at next safepoint.
829 // So we can miss this poll, but stop at next.
830
831 // Load dependent store, it must not pass loading of safepoint_id.
832 thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store
833
834 // This part we can skip if we notice we miss or are in a future safepoint.
835 OrderAccess::storestore();
836 // Load in wait barrier should not float up
837 thread->set_thread_state_fence(_thread_blocked);
838
839 _wait_barrier->wait(static_cast<int>(safepoint_id));
840 assert(_state != _synchronized, "Can't be");
841
842 // If barrier is disarmed stop store from floating above loads in barrier.
843 OrderAccess::loadstore();
844 thread->set_thread_state(state);
845
846 // Then we reset the safepoint id to inactive.
847 thread->safepoint_state()->reset_safepoint_id(); // Release store
848
849 OrderAccess::fence();
850
851 break;
852
853 default:
854 fatal("Illegal threadstate encountered: %d", state);
855 }
856 guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter,
857 "The safepoint id should be set only in block path");
858
859 // Check for pending. async. exceptions or suspends - except if the
860 // thread was blocked inside the VM. has_special_runtime_exit_condition()
861 // is called last since it grabs a lock and we only want to do that when
862 // we must.
863 //
864 // Note: we never deliver an async exception at a polling point as the
865 // compiler may not have an exception handler for it. The polling
866 // code will notice the async and deoptimize and the exception will
867 // be delivered. (Polling at a return point is ok though). Sure is
868 // a lot of bother for a deprecated feature...
869 //
870 // We don't deliver an async exception if the thread state is
871 // _thread_in_native_trans so JNI functions won't be called with
872 // a surprising pending exception. If the thread state is going back to java,
873 // async exception is checked in check_special_condition_for_native_trans().
874
875 if (state != _thread_blocked_trans &&
876 state != _thread_in_vm_trans &&
877 thread->has_special_runtime_exit_condition()) {
878 thread->handle_special_runtime_exit_condition(
879 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
880 }
881
882 // cross_modify_fence is done by SafepointMechanism::block_if_requested_slow
883 // which is the only caller here.
884 }
885
886 // ------------------------------------------------------------------------------------------------------
887 // Exception handlers
888
889
890 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
891 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
892 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
893 if (!ThreadLocalHandshakes) {
894 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
895 }
896
897 if (log_is_enabled(Info, safepoint, stats)) {
898 Atomic::inc(&_nof_threads_hit_polling_page);
899 }
900
901 ThreadSafepointState* state = thread->safepoint_state();
902
903 state->handle_polling_page_exception();
904 }
905
906
907 void SafepointSynchronize::print_safepoint_timeout() {
908 if (!timeout_error_printed) {
909 timeout_error_printed = true;
910 // Print out the thread info which didn't reach the safepoint for debugging
911 // purposes (useful when there are lots of threads in the debugger).
912 LogTarget(Warning, safepoint) lt;
913 if (lt.is_enabled()) {
914 ResourceMark rm;
915 LogStream ls(lt);
916
917 ls.cr();
918 ls.print_cr("# SafepointSynchronize::begin: Timeout detected:");
919 ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
920 ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
921 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
922 if (cur_thread->safepoint_state()->is_running()) {
923 ls.print("# ");
924 cur_thread->print_on(&ls);
925 ls.cr();
926 }
927 }
928 ls.print_cr("# SafepointSynchronize::begin: (End of list)");
929 }
930 }
931
932 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
933 // ShowMessageBoxOnError.
934 if (AbortVMOnSafepointTimeout) {
935 // Send the blocking thread a signal to terminate and write an error file.
936 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
937 if (cur_thread->safepoint_state()->is_running()) {
938 if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) {
939 break; // Could not send signal. Report fatal error.
940 }
941 // Give cur_thread a chance to report the error and terminate the VM.
942 os::sleep(Thread::current(), 3000, false);
943 }
944 }
945 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
946 SafepointTimeoutDelay, VMThread::vm_operation()->name());
947 }
948 }
949
950 // -------------------------------------------------------------------------------------------------------
951 // Implementation of ThreadSafepointState
952
953 ThreadSafepointState::ThreadSafepointState(JavaThread *thread)
954 : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false),
955 _safepoint_id(SafepointSynchronize::InactiveSafepointCounter),
956 _orig_thread_state(_thread_uninitialized), _next(NULL) {
957 }
958
959 void ThreadSafepointState::create(JavaThread *thread) {
960 ThreadSafepointState *state = new ThreadSafepointState(thread);
961 thread->set_safepoint_state(state);
962 }
963
964 void ThreadSafepointState::destroy(JavaThread *thread) {
965 if (thread->safepoint_state()) {
966 delete(thread->safepoint_state());
967 thread->set_safepoint_state(NULL);
968 }
969 }
970
971 uint64_t ThreadSafepointState::get_safepoint_id() const {
972 return OrderAccess::load_acquire(&_safepoint_id);
973 }
974
975 void ThreadSafepointState::reset_safepoint_id() {
976 OrderAccess::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter);
977 }
978
979 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) {
980 OrderAccess::release_store(&_safepoint_id, safepoint_id);
981 }
982
983 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) {
984 assert(is_running(), "better be running or just have hit safepoint poll");
985
986 JavaThreadState stable_state;
987 if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) {
988 // We could not get stable state of the JavaThread.
989 // Consider it running and just return.
990 return;
991 }
992
993 // Save the state at the start of safepoint processing.
994 _orig_thread_state = stable_state;
995
996 // Check for a thread that is suspended. Note that thread resume tries
997 // to grab the Threads_lock which we own here, so a thread cannot be
998 // resumed during safepoint synchronization.
999
1000 // We check to see if this thread is suspended without locking to
1001 // avoid deadlocking with a third thread that is waiting for this
1002 // thread to be suspended. The third thread can notice the safepoint
1003 // that we're trying to start at the beginning of its SR_lock->wait()
1004 // call. If that happens, then the third thread will block on the
1005 // safepoint while still holding the underlying SR_lock. We won't be
1006 // able to get the SR_lock and we'll deadlock.
1007 //
1008 // We don't need to grab the SR_lock here for two reasons:
1009 // 1) The suspend flags are both volatile and are set with an
1010 // Atomic::cmpxchg() call so we should see the suspended
1011 // state right away.
1012 // 2) We're being called from the safepoint polling loop; if
1013 // we don't see the suspended state on this iteration, then
1014 // we'll come around again.
1015 //
1016 bool is_suspended = _thread->is_ext_suspended();
1017 if (is_suspended) {
1018 account_safe_thread();
1019 return;
1020 }
1021
1022 if (safepoint_safe_with(_thread, stable_state)) {
1023 check_for_lazy_critical_native(_thread, stable_state);
1024 account_safe_thread();
1025 return;
1026 }
1027
1028 // All other thread states will continue to run until they
1029 // transition and self-block in state _blocked
1030 // Safepoint polling in compiled code causes the Java threads to do the same.
1031 // Note: new threads may require a malloc so they must be allowed to finish
1032
1033 assert(is_running(), "examine_state_of_thread on non-running thread");
1034 return;
1035 }
1036
1037 void ThreadSafepointState::account_safe_thread() {
1038 SafepointSynchronize::decrement_waiting_to_block();
1039 if (_thread->in_critical()) {
1040 // Notice that this thread is in a critical section
1041 SafepointSynchronize::increment_jni_active_count();
1042 }
1043 DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());)
1044 assert(!_safepoint_safe, "Must be unsafe before safe");
1045 _safepoint_safe = true;
1046 }
1047
1048 void ThreadSafepointState::restart() {
1049 assert(_safepoint_safe, "Must be safe before unsafe");
1050 _safepoint_safe = false;
1051 }
1052
1053 void ThreadSafepointState::print_on(outputStream *st) const {
1054 const char *s = _safepoint_safe ? "_at_safepoint" : "_running";
1055
1056 st->print_cr("Thread: " INTPTR_FORMAT
1057 " [0x%2x] State: %s _at_poll_safepoint %d",
1058 p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint);
1059
1060 _thread->print_thread_state_on(st);
1061 }
1062
1063 void ThreadSafepointState::print() const { print_on(tty); }
1064
1065 // ---------------------------------------------------------------------------------------------------------------------
1066
1067 // Block the thread at poll or poll return for safepoint/handshake.
1068 void ThreadSafepointState::handle_polling_page_exception() {
1069
1070 // If we're using a global poll, then the thread should not be
1071 // marked as safepoint safe yet.
1072 assert(!SafepointMechanism::uses_global_page_poll() || !_safepoint_safe,
1073 "polling page exception on thread safepoint safe");
1074
1075 // Step 1: Find the nmethod from the return address
1076 address real_return_addr = thread()->saved_exception_pc();
1077
1078 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1079 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1080 CompiledMethod* nm = (CompiledMethod*)cb;
1081
1082 // Find frame of caller
1083 frame stub_fr = thread()->last_frame();
1084 CodeBlob* stub_cb = stub_fr.cb();
1085 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1086 RegisterMap map(thread(), true);
1087 frame caller_fr = stub_fr.sender(&map);
1088
1089 // Should only be poll_return or poll
1090 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1091
1092 // This is a poll immediately before a return. The exception handling code
1093 // has already had the effect of causing the return to occur, so the execution
1094 // will continue immediately after the call. In addition, the oopmap at the
1095 // return point does not mark the return value as an oop (if it is), so
1096 // it needs a handle here to be updated.
1097 if( nm->is_at_poll_return(real_return_addr) ) {
1098 // See if return type is an oop.
1099 bool return_oop = nm->method()->is_returning_oop();
1100 Handle return_value;
1101 if (return_oop) {
1102 // The oop result has been saved on the stack together with all
1103 // the other registers. In order to preserve it over GCs we need
1104 // to keep it in a handle.
1105 oop result = caller_fr.saved_oop_result(&map);
1106 assert(oopDesc::is_oop_or_null(result), "must be oop");
1107 return_value = Handle(thread(), result);
1108 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1109 }
1110
1111 // Block the thread
1112 SafepointMechanism::block_if_requested(thread());
1113
1114 // restore oop result, if any
1115 if (return_oop) {
1116 caller_fr.set_saved_oop_result(&map, return_value());
1117 }
1118 }
1119
1120 // This is a safepoint poll. Verify the return address and block.
1121 else {
1122 set_at_poll_safepoint(true);
1123
1124 // verify the blob built the "return address" correctly
1125 assert(real_return_addr == caller_fr.pc(), "must match");
1126
1127 // Block the thread
1128 SafepointMechanism::block_if_requested(thread());
1129 set_at_poll_safepoint(false);
1130
1131 // If we have a pending async exception deoptimize the frame
1132 // as otherwise we may never deliver it.
1133 if (thread()->has_async_condition()) {
1134 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1135 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1136 }
1137
1138 // If an exception has been installed we must check for a pending deoptimization
1139 // Deoptimize frame if exception has been thrown.
1140
1141 if (thread()->has_pending_exception() ) {
1142 RegisterMap map(thread(), true);
1143 frame caller_fr = stub_fr.sender(&map);
1144 if (caller_fr.is_deoptimized_frame()) {
1145 // The exception patch will destroy registers that are still
1146 // live and will be needed during deoptimization. Defer the
1147 // Async exception should have deferred the exception until the
1148 // next safepoint which will be detected when we get into
1149 // the interpreter so if we have an exception now things
1150 // are messed up.
1151
1152 fatal("Exception installed and deoptimization is pending");
1153 }
1154 }
1155 }
1156 }
1157
1158
1159 // -------------------------------------------------------------------------------------------------------
1160 // Implementation of SafepointTracing
1161
1162 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0;
1163 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0;
1164 jlong SafepointTracing::_last_safepoint_cleanup_time_ns = 0;
1165 jlong SafepointTracing::_last_safepoint_end_time_ns = 0;
1166 jlong SafepointTracing::_last_safepoint_end_time_epoch_ms = 0;
1167 jlong SafepointTracing::_last_app_time_ns = 0;
1168 int SafepointTracing::_nof_threads = 0;
1169 int SafepointTracing::_nof_running = 0;
1170 int SafepointTracing::_page_trap = 0;
1171 VM_Operation::VMOp_Type SafepointTracing::_current_type;
1172 jlong SafepointTracing::_max_sync_time = 0;
1173 jlong SafepointTracing::_max_vmop_time = 0;
1174 uint64_t SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0};
1175
1176 void SafepointTracing::init() {
1177 // Application start
1178 _last_safepoint_end_time_ns = os::javaTimeNanos();
1179 // amount of time since epoch
1180 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis();
1181 }
1182
1183 // Helper method to print the header.
1184 static void print_header(outputStream* st) {
1185 // The number of spaces is significant here, and should match the format
1186 // specifiers in print_statistics().
1187
1188 st->print("VM Operation "
1189 "[ threads: total initial_running ]"
1190 "[ time: sync cleanup vmop total ]");
1191
1192 st->print_cr(" page_trap_count");
1193 }
1194
1195 // This prints a nice table. To get the statistics to not shift due to the logging uptime
1196 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none
1197 void SafepointTracing::statistics_log() {
1198 LogTarget(Info, safepoint, stats) lt;
1199 assert (lt.is_enabled(), "should only be called when printing statistics is enabled");
1200 LogStream ls(lt);
1201
1202 static int _cur_stat_index = 0;
1203
1204 // Print header every 30 entries
1205 if ((_cur_stat_index % 30) == 0) {
1206 print_header(&ls);
1207 _cur_stat_index = 1; // wrap
1208 } else {
1209 _cur_stat_index++;
1210 }
1211
1212 ls.print("%-28s [ "
1213 INT32_FORMAT_W(8) " " INT32_FORMAT_W(8) " "
1214 "]",
1215 VM_Operation::name(_current_type),
1216 _nof_threads,
1217 _nof_running);
1218 ls.print("[ "
1219 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " "
1220 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]",
1221 (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns),
1222 (int64_t)(_last_safepoint_cleanup_time_ns - _last_safepoint_sync_time_ns),
1223 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns),
1224 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns));
1225
1226 ls.print_cr(INT32_FORMAT_W(16), _page_trap);
1227 }
1228
1229 // This method will be called when VM exits. This tries to summarize the sampling.
1230 // Current thread may already be deleted, so don't use ResourceMark.
1231 void SafepointTracing::statistics_exit_log() {
1232 if (!log_is_enabled(Info, safepoint, stats)) {
1233 return;
1234 }
1235 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1236 if (_op_count[index] != 0) {
1237 log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1238 _op_count[index]);
1239 }
1240 }
1241
1242 log_info(safepoint, stats)("VM operations coalesced during safepoint " INT64_FORMAT,
1243 VMThread::get_coalesced_count());
1244 log_info(safepoint, stats)("Maximum sync time " INT64_FORMAT" ns",
1245 (int64_t)(_max_sync_time));
1246 log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation) "
1247 INT64_FORMAT " ns",
1248 (int64_t)(_max_vmop_time));
1249 }
1250
1251 void SafepointTracing::begin(VM_Operation::VMOp_Type type) {
1252 _op_count[type]++;
1253 _current_type = type;
1254
1255 // update the time stamp to begin recording safepoint time
1256 _last_safepoint_begin_time_ns = os::javaTimeNanos();
1257 _last_safepoint_sync_time_ns = 0;
1258 _last_safepoint_cleanup_time_ns = 0;
1259
1260 _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns;
1261 _last_safepoint_end_time_ns = 0;
1262
1263 RuntimeService::record_safepoint_begin(_last_app_time_ns);
1264 }
1265
1266 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) {
1267 _last_safepoint_sync_time_ns = os::javaTimeNanos();
1268 _nof_threads = nof_threads;
1269 _nof_running = nof_running;
1270 _page_trap = traps;
1271 RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns);
1272 }
1273
1274 void SafepointTracing::cleanup() {
1275 _last_safepoint_cleanup_time_ns = os::javaTimeNanos();
1276 }
1277
1278 void SafepointTracing::end() {
1279 _last_safepoint_end_time_ns = os::javaTimeNanos();
1280 // amount of time since epoch
1281 _last_safepoint_end_time_epoch_ms = os::javaTimeMillis();
1282
1283 if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) {
1284 _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns;
1285 }
1286 if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) {
1287 _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns;
1288 }
1289 if (log_is_enabled(Info, safepoint, stats)) {
1290 statistics_log();
1291 }
1292
1293 log_info(safepoint)(
1294 "Safepoint \"%s\", "
1295 "Time since last: " JLONG_FORMAT " ns, "
1296 "Reaching safepoint: " JLONG_FORMAT " ns, "
1297 "At safepoint: " JLONG_FORMAT " ns, "
1298 "Total: " JLONG_FORMAT " ns",
1299 VM_Operation::name(_current_type),
1300 _last_app_time_ns,
1301 _last_safepoint_cleanup_time_ns - _last_safepoint_begin_time_ns,
1302 _last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns,
1303 _last_safepoint_end_time_ns - _last_safepoint_begin_time_ns
1304 );
1305
1306 RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns);
1307 }